The MADS box is a conserved

sequence motif In biology, a sequence motif is a nucleotide or amino-acid sequence pattern that is widespread and usually assumed to be related to biological function of the macromolecule. For example, an ''N''-glycosylation site motif can be defined as ' ...

. The genes which contain this motif are called the MADS-box gene family. The MADS box encodes the DNA-binding MADS domain. The MADS domain binds to DNA sequences of high similarity to the motif CC /Tsub>6GG termed the CArG-box. MADS-domain proteins are generally

transcription factors In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The fun ...

. The length of the MADS-box reported by various researchers varies somewhat, but typical lengths are in the range of 168 to 180 base pairs, i.e. the encoded MADS domain has a length of 56 to 60 amino acids. There is evidence that the MADS domain evolved from a sequence stretch of a

type II topoisomerase Type II topoisomerases are topoisomerases that cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils. They use the hydrolysis of ATP, unlike Type I topoisomerase. In this process, these enzymes change th ...

in a common ancestor of all extant eukaryotes.

Origin of name and history of research

The first MADS-box gene to be identified was ''ARG80'' from budding yeast, ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have b ...

'', but was at that time not recognized as a member of a large gene family. The MADS-box gene family got its name later as an acronym referring to the four founding members, ignoring ''ARG80'': * MCM1 from the budding yeast, ''

'', * AGAMOUS from the thale cress ''

Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter ...

'', * DEFICIENS from the snapdragon ''

Antirrhinum majus ''Antirrhinum majus'', the common snapdragon (often - especially in horticulture - simply "snapdragon"), is a species of flowering plant belonging to the genus ''Antirrhinum''. The plant was placed in the family Plantaginaceae following a revis ...

'', * SRF from the human ''

Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture ...

''. In ''A. thaliana'', ''A. majus'', and ''

Zea mays Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The ...

'' this motif is involved in floral development. Early study in these model angiosperms was the beginning of research into the

molecular evolution Molecular evolution is the process of change in the sequence composition of cellular molecules such as DNA, RNA, and proteins across generations. The field of molecular evolution uses principles of evolutionary biology and population genet ...

of floral structure in general, as well as their role in nonflowering plants.

Diversity

MADS-box genes were detected in nearly all eukaryotes studied. While the genomes of animals and fungi generally possess only around one to five MADS-box genes, genomes of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants t ...

s have around 100 MADS-box genes. Two types of MADS-domain proteins are distinguished; the SRF-like or Type I MADS-domain proteins and the MEF2-like (after MYOCYTE-ENHANCER-FACTOR2) or Type II MADS-domain proteins. SRF-like MADS-domain proteins in animals and fungi have a second conserved domain, the SAM (SRF, ARG80, MCM1) domain. MEF2-like MADS-domain proteins in animals and fungi have the MEF2 domain as a second conserved domain. In plants, the MEF2-like MADS-domain proteins are also termed MIKC-type proteins referring to their conserved domain structure, where the MADS (M) domain is followed by an Intervening (I), a Keratin-like (K) and a

C-terminal domain The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain ( protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...

. In plants, MADS-domain protein form tetramers and this is thought to be central for their function. The structure of the tetramerisation domain of the MADS-domain protein SEPALLATA3 was solved illustrating the structural basis for tetramer formation A

geneticist A geneticist is a biologist or physician who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a scientist or a lecturer. Geneticists may perform general research on genetic processes ...

intensely investigating MADS-box genes is Günter Theißen at the

University of Jena The University of Jena, officially the Friedrich Schiller University Jena (german: Friedrich-Schiller-Universität Jena, abbreviated FSU, shortened form ''Uni Jena''), is a public research university located in Jena, Thuringia, Germany. The ...

. For example, he and his coworkers have used these genes to show that the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

Gnetales is more closely related to the

conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ext ...

than to the

s. MADS-box is under-studied in wheat . In ''

'' the mutant '' Tunicate1'' produces

pod corn Pod corn or wild maize is a variety of maize. It is not a wild ancestor of maize but rather a mutant that forms leaves around each kernel. Pod corn (''tunicata'' Sturt) is not grown commercially, but it is preserved in some localities. Pod corn ...

. ''Tunicate1'' is a mutant of '' Z. mays MADS19'' (''ZMM19''), in the '' SHORT VEGETATIVE PHASE'' gene family. ''ZMM19'' can be ectopically expressed. Such ectopic expression of ''ZMM19'' in ''A. thaliana'' enlarges

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coine ...

s, suggesting

conservation Conservation is the preservation or efficient use of resources, or the conservation of various quantities under physical laws. Conservation may also refer to: Environment and natural resources * Nature conservation, the protection and manageme ...

Function of MADS-box genes

MADS-box genes have a variety of functions. In animals, MADS-box genes are involved in muscle development and

cell proliferation Cell proliferation is the process by which ''a cell grows and divides to produce two daughter cells''. Cell proliferation leads to an exponential increase in cell number and is therefore a rapid mechanism of tissue growth. Cell proliferation r ...

and differentiation. Functions in fungi range from pheromone response to

arginine Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the am ...

metabolism. In plants, MADS-box genes are involved in controlling all major aspects of development, including male and female

gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the ...

development, embryo and seed development, as well as root, flower and fruit development. Some MADS-box genes of flowering plants have homeotic functions like the

HOX genes Hox genes, a subset of homeobox genes, are a group of related genes that specify regions of the body plan of an embryo along the head-tail axis of animals. Hox proteins encode and specify the characteristics of 'position', ensuring that the co ...

of animals. The floral homeotic MADS-box genes (such as ''AGAMOUS'' and ''DEFICIENS'') participate in the determination of floral organ identity according to the

ABC model of flower development The ABC model of flower development is a scientific model of the process by which flowering plants produce a pattern of gene expression in meristems that leads to the appearance of an organ oriented towards sexual reproduction, a flower. There a ...

. Another function of MADS-box genes is flowering time determination. In ''

'' the MADS box genes ''SOC1'' and ''

Flowering Locus C Flowering Locus C (''FLC'') is a MADS-box gene that in late-flowering ecotypes of the plant ''Arabidopsis thaliana'' is responsible for vernalization. In a new seedling ''FLC'' is expressed, which prevents flowering. Upon exposure to cold, less ' ...

'' (''FLC'') have been shown to have an important role in the integration of molecular flowering time pathways. These genes are essential for the correct timing of ''

flowering A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

'', and help to ensure that fertilization occurs at the time of maximal reproductive potential.

Structure of MADS-box proteins

The MADS box protein structure is characterized by four domains. At the N terminal end is the highly conserved MADS

DNA binding domain A DNA-binding domain (DBD) is an independently folded protein domain that contains at least one structural motif that recognizes double- or single-stranded DNA. A DBD can recognize a specific DNA sequence (a recognition sequence) or have a genera ...

. Next to the MADS domain is the moderately conserved Intervening (I) and

Keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up Scale (anatomy), scales, hair, Nail ...

-like (K) domains, which are involved in specific protein-protein interactions. The

carboxyl terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain ( protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...

heterodimer In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' ha ...

s and

multimeric protein A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Protein complexes are distinct from multienzyme complexes, in which multiple catalytic domains are found in a single polypeptide chain. Protein ...

complexes.

References

External links

M type MADS family
a
PlantTFDB: Plant Transcription Factor DatabaseMIKC type MADS family
a
PlantTFDB: Plant Transcription Factor Database
{{DEFAULTSORT:Mads-Box Genes Proteins Developmental biology